Catalyzed fast cure polyurethane sealant composition

ABSTRACT

A polyurethane sealant composition is made from a polyurethane prepolymer having blocked isocyanate groups. A bicyclic amidine catalyst is utilized in association with an amine curing agent having at least two primary amine groups to achieve a relatively fast cure time. In the first embodiment, the catalyst is 1,8-diazobicyclo (5:4:0) undecene-7 (DBU), whereas in a second embodiment the catalyst is 1,5-diazobicyclo (4:3:0) non-5-ene (DBN).

CROSS-REFERENCE

This application is a continuation-in-part application of U.S. Pat.application Ser. No. 07/030,773, filed Mar. 25, 1987 for "Catalyzed FastCure Polyurethane Sealant Composition," Steven L. Hannah, et al, nowU.S. Pat. No. 4,798,879.

FIELD OF THE INVENTION

The present invention relates to a bicyclic amidine catalyst forunblocking isocyanate groups of a polyurethane prepolymer. Morespecifically, the present invention relates to the use of1,8-diazobicyclo (5:4:0) undecene-7 (DBU), derivatives thereof, or1,5-diazobicyclo (4:3:0) non-5-ene (DBN) or derivatives thereof as acatalyst in a polyurethane sealant composition.

BACKGROUND

Heretofore various sealant compositions have been proposed. For example,U.S. Pat. No. 3,248,371 relates to a blocked isocyanate-terminatedcoating composition which is unblocked by reacting with a hydroxytertiary amine.

U.S. Pat. No. 3,267,078 relates to a coating composition that contains ablocked isocyanate-terminated polyether-based urethane intermediate andwhich is reacted with a diimine prepared by reacting a diamine with acarbonyl compound such as a ketone or an aldehyde.

U.S. Pat. No. 3,940,542 to Knopf et al relates to a method for theproduction of water swellable fibers extruded from an isocyanatoterminated prepolymer and an organic diisocyanate into a crosslinkingbath.

SUMMARY OF THE INVENTION

Sealant compositions desirably have a combination of properties whichrender them particularly suitable for their intended applications. Suchcompositions should be able to ba packaged in sealed containers orcartridges and stored for relatively long periods of time withoutobjectionably "setting up" or hardening (as a result of crosslinking).When applied as a caulking sealant composition, they should form arelatively tack-free surface soon after being applied and exposed toatmospheric moisture and should cure without the formation of bubbleswithin an acceptable time period. They should also adhere tenaciously inthe cured state to a wide variety of surfaces, such as to glass,aluminum, concrete, marble and steel surfaces. The sealant in the curedstate should have sufficient elasticity and flexibility to withstandexpansions and contractions of panels, etc. with which it is associatedduring temperature variations experienced as a result of climaticchanges and to withstand wind forces that cause panels with which it isassociated to flex or twist.

It is therefore an aspect of the present invention to provide a fastcure polyurethane sealant composition.

It is a further aspect of the present invention to provide a fast curepolyurethane sealant system, as above, wherein an unblocking bicyclicamidine catalyst is utilized.

It is another aspect of the present invention to provide a fast curepolyurethane sealant composition, as above, wherein the prepolymer ismade from a polyether polyol intermediate and a polyisocyanate with theisocyanate groups being subsequently blocked so that the prepolymer hasa relatively long shelf life.

It is yet another aspect of the present invention to provide a fast curepolyurethane sealant composition, as above, wherein a variety of aminecuring agents having at least two primary amine groups therein can beutilized.

It is yet another aspect of the present invention to provide a fast curepolyurethane sealant composition, as above, wherein additives can beutilized such as thixotropes, alcohols, and other hydroxyl species whichcould not normally otherwise be utilized as they would react with freeisocyanates.

It is yet another aspect of the present invention to provide a fast curepolyurethane sealant composition, as above, wherein cure of thecomposition can be controlled from essentially instantaneous to one ortwo hours or longer by varying the amount of catalyst utilized.

It is yet another aspect of the present invention to provide a fast curepolyurethane sealant composition, as above, wherein cure occurs atambient temperatures.

These and other aspects of the present invention will be betterunderstood by reference to the following detailed disclosure.

In general, a curable polyurethane composition comprises a polyurethaneprepolymer component, said polyurethane prepolymer component being madefrom a polyester polyol, a polybutadiene polyol, or a poly(oxyalkylene)polyol and an aromatic polyisocyanate, said alkylene group of saidpoly(oxyalkylene) polyol having from 2 to 6 carbon atoms, saidpolyurethane prepolymer having blocked isocyanate groups; a curing agentcomponent, said curing agent component comprising an amine curing agentcontaining at least two primary amines, and an amount of a bicyclicamidine catalyst or a derivative thereof capable of unblocking saidblocked isocyanate groups, and wherein said amount is an effectiveamount to effect a cure within an hour at ambient temperature.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a curable polyurethane compositionwhich contains two different components, that is a polyurethaneprepolymer component as well as a curing agent component. The componentsare separately maintained from one another and are brought togethergenerally at the application site whereupon cure readily occurs in ashort period of time.

The prepolymer is made by reacting a hydroxyl terminated intermediatewith a polyisocyanate. The hydroxyl terminated intermediate can be anyconventional polyester polyol or a conventional polybutadiene polyol.Desirably, the hydroxyl terminated intermediate is a polyether polyol.More specifically, a poly(oxyalkylene) diol or triol is utilized whereinthe alkylene group contains from 2 to 6 carbon atoms with 3 carbon atomsbeing preferred. Thus, poly(oxypropylene) diol or triol can be utilizedwith the latter being highly preferred. Suitable polyether polyols thusinclude polyethylene ether triol, polypropylene ether triol,polybutylene ether triol, and the like. In lieu of the above triolpolyethers, the corresponding diol polyether can be utilized. Theequivalent weight of the various hydroxyl terminated intermediates isfrom about 500 to about 10,000, desirably from about 500 to about 3,000,and preferably from about 1,000 to about 2,100. Such intermediates thusgenerally have a long flexible backbone which is desired for use in thepresent invention.

An optional, although often preferred, aspect of the polyether polyolsof the present invention is that they are end capped with ethylene oxideend blocks. The provision of ethylene oxide end blocks provides aprimary hydroxyl group which tends to be more reactive withpolyisocyanate than the polyether polyol. The total amount of theethylene oxide end caps is rather small, that is generally 10 percent orless by weight, and preferably 5 percent or less by weight based uponthe total weight of the end capped polyethylene polyol. Amounts inexcess of approximately 5 percent by weight of ethylene oxide end blocksare avoided since the intermediate tends to become moisture sensitive.

The polyisocyanates which can be utilized in the present inventiondesirably contain aromatic groups since aliphatic polyisocyanatesgenerally cannot be unblocked and usually are not reactive. The aromaticpolyisocyanate can generally be represented by the formula R--NCO)nwherein n is 2 or 3 with 2 being highly preferred. R is an aromatic oran alkyl substituted aromatic containing from about 6 to about 20 carbonatoms, with from 6 to about 15 carbon atoms being desired. Examples ofspecific aromatic polyisocyanates include the various diphenyl methaneisocyanates, the various naphthalene diisocyanates such as naphthalene1,5-diisocyanate, the various tolylene diisocyanates such as2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, the variousphenylene diisocyanates, the various toluene diisocyanates such astoluene-2,4-diisocyanate, the various biphenylene diisocyanates, andcombinations thereof. A preferred polyisocyanate of the presentinvention is toluene diisocyanate.

The polyurethane prepolymer is readily prepared by mixing the polyetherpolyol with the polyisocyanate at ambient temperature and pressurealthough desirably the reaction is carried out at elevated temperatures,such as from about 60° C. to about 100° C. since the reaction rate issignificantly increased. The equivalent ratio of the polyisocyanate tothe polyether polyol can be from about 0.8 to about 3.0. However, aslight excess is preferred to ensure complete reaction of the terminalhydroxy groups.

In order to provide a polymer that is more stable during storage, theisocyanate-terminated prepolymer described above is "blocked" with ablocking agent that reacts with the terminal isocyanate groups of theprepolymer. Blocking agents useful in the present invention include anyof the conventional blocking agents as well as those known to the artand to the literature that produce blocked terminal isocyanates that donot react readily with moisture in air at room temperature (25° C.), butwhich will be readily "unblocked" and quickly or rapidly react with acurative of the present invention at room temperature. Such blockingagents include phenol, 3-methoxyphenol, 4-methoxyphenol, nonylphenol,metacresol, para-cresol, 4-chlorophenol, meta-hydroxybenzaldehyde,ortho-hydroxybenzaldehyde, para-hydroxybenzaldehyde, hydroquinone,1-hydroxy-2-propanone, 3-hydroxyacetophenone, 4-hydroxyacetophenone,ethyl acetyl acetate and cyclohexanone oxime. Sufficient blocking agentis reacted with the isocyanate-terminated polymer to theoretically"block" all of the terminal isocyanates, e.g. an equivalent excess, ofthe polymer. Generally, at least a 10 percent equivalent excess isutilized.

The polyurethane prepolymer of the present invention is cured with anyconventional amine curing agent as well as those known to the art and tothe literature which contain at least two primary amine groups therein.The amine curing agents can be compounds having from 3 to about 260carbon atoms therein or desirably from about 6 to about 36 carbon atoms.Additionally, the amine curing agents can be a polymer having amolecular weight up to about 5,000 and desirably from about 200 to about450. Examples of specific amine compounds include triethylene tetramine,bisaminopropylpiperazine (BAPP), diethylene triamine, tris(2-aminoethyl)amine, 2-methyl pentamethylene diamine, isophorone diamine, and thelike.

Various polymeric amines can be utilized such as the various Jeffaminesproduced by the Texaco Chemical Company. A desired polymeric amine arethe Jeffamine D-400 compounds which generally have the following formula##STR1## wherein n is 5 or 6. Numerous other polymeric amine compoundscan be utilized such as the various other Jeffamine D series compoundswherein n varies from 2 to about 70, and other types of Jeffamines. Asnoted above, the basic requirement is that the amine curing agentcontain at least two primary amine groups therein whether it be an aminecompound or a polymeric amine compound.

Although various amine curing agents of the present invention can beutilized, including various combinations thereof, a desired amine curingagent is a blend of the Jeffamine D-400 amines and BAPP in relativelyequal equivalent amounts of each compound, for example, from about 0.8to about 1.2 equivalents of one compound based upon one equivalent ofthe remaining compound.

The amount of the amine curing agent containing at least two primaryamines therein is from about 0.8 to about 1.2 equivalents and desirablyabout 1 equivalent for each blocked isocyanate equivalent.

Although the amine curing agents of the present invention are effectivein removing the blocking agents and thus permitting the polyurethaneprepolymer to cure, the time is generally slow as often from a few hoursto many days. However, according to the concepts of the presentinvention, it has been found that a particular catalyst and variousderivatives thereof, e.g. a reaction product, are effective in quicklyremoving the blocking agents thereby permitting the amine curing agentto rapidly cure the polyurethane prepolymer in a very short period oftime, generally within a couple hours, desirably within an hour, andpossibly within a matter of minutes. The effective catalyst of thepresent invention is a bicyclic amidine and in the first embodiment is1,8-diazobicyclo (5:4:0) undecene-7, that is DBU, and generally has theformula ##STR2##

In a second embodiment, the catalyst is1,5-diazobicyclo(4:3:0)non-5-ene, that is DBN, and generally has thefollowing formula ##STR3##

The various derivatives or reaction products of the bicyclic amidinewhich can be utilized in the present invention as a catalyst include thereaction product of DBU or DBN with phenol, as well as with variousother acidic compounds. Such acidic compounds include the varioussulfonic acids such as p-toluenesulfonic, sulfimides, sulfamides,phosphonic acids, the various N-sulfonylcarboxamides which have a totalof from 2 to about 36 carbon atoms, and the various carboxylic acidswhich have a total of from 2 to 18 carbon atoms. The reaction productwith phenol is desired whereas the unreacted catalyst DBU or DBN ispreferred.

The amount of the unblocking catalyst often depends upon the applicationand desired end result since larger amounts of catalyst generally effecta quicker cure time. That is, amounts can be utilized to effect a curein an hour or two or in a matter of minutes. Still higher amounts caneffect cure almost instantaneously. Generally, the amount of catalystcan range from about 0.01 to about 2.5 parts, desirably from about 0.02to about 1.2 parts, and preferably from about 0.1 to about 0.25 part byweight per 100 parts by weight of prepolymer.

As noted, the polyurethane sealant composition of the present inventionis generally contained as two separate components. That is a prepolymeror base component and a curing agent component. The curing agentcomponent generally contains the amine curing agent, the bicyclicamidine catalyst or derivative thereof, as well as optionalplasticizers, pigments, thickeners, drying agents, and the like. Thebase component contains the prepolymer as well as various conventionaladditives or compounding ingredients such as fillers, thickeners, orthixotropic agents, pigments, plasticizers, UV absorbers, solvents, andthe like.

The base component generally contains large amounts, that is from about60 to about 200 parts by weight per 100 parts by weight of prepolymer ofa filler such as talc, various silicates, various clays, calciumcarbonate, and the like. The thickening agents are generally thixotropiccompounds such as hydrogenated castor oils, fumed silica, crosslinkedacrylates, and the like, and utilized in amounts of from about 10 toabout 30 parts per 100 parts by weight of prepolymer. The amount of UVabsorbers are generally very small, usually less than 1 or 2 parts byweight per 100 parts by weight of prepolymer and include the varioushindered amines, benzotriazoles, and hindered phenols. The plasticizerscan include the various phthalates, the various adipates such as dioctyladipate, dipropylene glycol dibenzoate, and the like, in amounts of fromabout 15 to about 50 parts by weight per 100 parts by weight ofprepolymer. Solvents are generally utilized to adjust the viscosity ofthe prepolymer or base component to a desired range and constitute lessthan 10 percent volatility of the total composition. Suitable solventsinclude naphthalene, toluene, xylene, and the like. Pigments such astitanium dioxide, iron oxides, carbon black, and the like, can beutilized in suitable amounts to achieve a desired color.

It is noted that the curing agent component can also contain some of theabove compounds such as the fillers, the thickening agents, theplasticizers, the pigments, and the like.

The amount of the prepolymer component with respect to the curing agentcomponent can vary over a wide range depending upon a desired end usewith a preferred range often being from about 10 parts to about 12 partsby weight of the prepolymer component per 1 part by weight of curingagent component. The polyurethane sealant composition of the presentinvention naturally is stored as two separate components. It is thencombined and immediately applied to a substrate, etc. to achieve adesired utility such as forming a sealant between curtain wall sections,between concrete, between stone, or between any construction material.

The polyurethane sealant composition of the present invention hascertain inherent advantages over conventional free isocyanates andpolyol cure systems in that the prepolymer component containing theblocked isocyanate prepolymer is more stable than free isocyanatesystems. Since the prepolymer component system is not predried orprereacted, it can contain additives that normally would react with freeisocyanate such as hydrogenated castor oil, alcohols, and the like. Thecure time can be adjusted from instantaneous, that is, a few seconds,hours or even longer, by varying the concentration of the catalyst. TheDBU and/or DBN compound or derivative of these are true catalysts andfinal properties are unaffected by the presence of such a catalyst.Other conventional urethane catalysts such as tin salts have been foundnot to work with regard to the blocked isocyanate prepolymer. The fastcure times of the present invention are accomplished at roomtemperature, that is at ambient or even sub-ambient temperatures as fromabout 0° C. to about 60° C., and preferably from about 20° C. to about30° C.

The polyurethane sealant compositions of the present invention will bebetter understood by reference to the following example.

EXAMPLE 1

A prepolymer component was prepared from the following compounds. Theurethane prepolymer was made from an ethylene oxide end capped(approximately 5 percent by weight) polyoxypropylene triol reacted withtoluene diisocyanate and subsequently blocked with nonyl phenol.

BASE COMPONENT FORMULATION

    ______________________________________                                        BASE COMPONENT FORMULATION                                                    Description of the Chem. Item                                                                         Parts by Weight                                       ______________________________________                                        6,000 molecular wt. trifunctional                                                                     100                                                   blocked isocyanate prepolymer                                                 Hydrogenated castor oil 14                                                    Calcium Carbonate       60                                                    Aliphatic Solvent, Naphtha                                                                            3                                                     Dipropylene Glycol Dibenzoate                                                                         20                                                    Pigment, Ti0.sub.2, carbon black, iron oxides                                                         8                                                     UV Stabilizer, benzotriazole/hindered amine                                                           0.5                                                   ______________________________________                                    

The prepolymer composition was prepared as follows: 331/3 parts of theurethane prepolymer was added to a clean caulk mixer rotating at 5 RPMalong with the UV stabilizers and the hydrogenated castor oil. Thecompounds were mixed at 20 RPM for 15 minutes until uniform and then anadditional 331/3 parts by weight of the prepolymer was added along withthe calcium carbonate. The compounds were then mixed for 15 minutes at20 RPM until well dispersed and examined for lumps. When no lumpsremained, the remaining 331/3 parts by weight of the prepolymer wasadded along with the plasticizer. The compounds were then mixed at 15RPM under heat until the temperature reached 125° F.-130° F. The mixerwas then cooled to 115° F. at which time the solvent was added. Mixingwas continued until a uniform blend was obtained.

The curing agent component had the following formulation.

CURING AGENT COMPONENT FORMULATION

    ______________________________________                                        CURING AGENT COMPONENT FORMULATION                                            Description       Weight Percent of Compound                                  ______________________________________                                        Dipropylene glycol dibenzoate                                                                   58                                                          Titanium dioxide  0.9                                                         Hydrophobic fumed silica                                                                        5.9                                                         Methyl trimethoxy silane                                                                        0.3                                                         BAPP              11                                                          Jeffamine D-400   23                                                          DBU               0.8                                                         ______________________________________                                    

The preparation of the curing component was as follows. Into a cleanmixer under a nitrogen atmosphere was charged the dipropylene glycoldibenzoate plasticizer, the titanium dioxide pigment, and the fumedsilica and mixed at 40 RPM for 5 minutes. The methyl trimethoxy silanedrying agent was then added and mixed at 20 RPM for about 10 minutes.The amine curing agent and the DBU catalyst were then added and mixed at20 RPM for about 10 minutes. A vacuum was pulled to 27 inches of mercuryuntil the composition was completely de-aired and packaged.

The base component and the curing agent component were mixed in thedesired stoichiometric proportion of 1 to 1, that is approximately 12parts by weight of the base component to approximately 1 part by weightof the curing agent component. The components were applied from a twocomponent meter-mix pump with a static mixing device on the nozzle. Themixed composition was then applied between aluminum and granite curtainwall sections and formed a sealed joint. The joint was flexible and goodadhesion was obtained within 20 minutes.

EXAMPLE 2

A similar example was run testing DBN in the catalyst using the basecomponent formation as recited in Example 1. DBN was substituted for DBUin the curing agent component formulation at the same level. Thecomponents were formulated and processed according to the descriptionfor Example 1. The results were comparable to the first example. Thejoint was flexible and good adhesion was obtained within twenty minutes.

The sealant compositions of the present invention have excellent storagestability in sealed containers, have excellent flowabilitycharacteristics and thus can be pumped or utilized in caulking guns,have good flexibility and pliability, do not shrink objectionally uponcuring, and have good adhesion to various primed substrates. Thesesealant compositions have an increased rate of cure as compared to priorart compounds. While the rate of cure is generally dependent upontemperature, it is also dependent upon amount of catalyst in the curingsystem. It is often preferable to add an effective amount of catalyst tocause cure within twenty minutes at ambient temperature, i.e., thetemperature of the environment in which the sealant is mixed andapplied. These temperatures may range from about 40° F. to about 95° F.

While in accordance with the Patent Statutes, the best mode andpreferred embodiment has been set forth, the scope of the invention isnot limited thereto, but rather by the scope of the attached claims.

What is claimed is:
 1. A curable polyurethane composition, comprising:apolyurethane prepolymer component, said polyurethane prepolymercomponent being made from a polyester polyol, a polybutadiene polyol, ora poly(oxyalkylene) polyol and an aromatic polyisocyanate, said alkylenegroup of said poly(oxyalkylene) polyol having from 2 to 6 carbon atoms,said polyurethane prepolymer having blocked isocyanate groups; a curingagent component, said curing agent component comprising an amine curingagent containing at least two primary amines, and an amount of abicyclic amidine catalyst or a derivative thereof capable of unblockingsaid blocked isocyanate groups, and wherein said amount is an effectiveamount to effect a cure within an hour at ambient temperature.
 2. Acurable polyurethane composition according to claim 2, wherein saidderivative of said catalyst is the reaction product of said catalystwith phenol, a sulfonic acid, a sulfimide, a sulfamide, a phosphonicacid, a N-sulfonylcarboxamide having a total of from 2 to 36 carbonatoms, or a carboxylic acid having from 2 to 18 carbon atoms, whereinsaid blocked urethane prepolymer is made with a blocking agentsubsequently blocking terminal isocyanate groups, and wherein the amountof said catalyst is from about 0.01 to about 2.5 parts by weight per 100parts by weight of said prepolymer.
 3. A curable polyurethanecomposition according to claim 1, wherein said derivative of saidbicyclic amidine catalyst is the reaction product of1,5-diazobicyclo(4:3:0)non-5-ene with phenol or 2-ethyl hexanoic acid.4. A curable polyurethane composition according to claim 3, wherein saidprepolymer is made from said poly(oxyalkylene) polyol, wherein saidpoly(oxyalkylene) polyol has an equivalent weight of from about 500 toabout 3,000, wherein said poly(oxyalkylene) polyol optionally hasethylene oxide end blocks with the total amount of said ethylene oxideend blocks being 10 percent by weight or less based upon the totalweight of said end blocked poly(oxyalkylene) polyol, wherein saidpolyisocyanate is an aromatic diisocyanate, and wherein said aminecuring agent contains a total of from 3 to about 260 carbon atoms or isa polymer having a molecular weight up to about 5,000.
 5. A curablepolyurethane composition according to claim 4, wherein the amount ofsaid catalyst is from about 0.02 to about 1.2 parts by weight per 100parts by weight of said prepolymer.
 6. A curable polyurethanecomposition according to claim 4, wherein said poly(oxyalkylene) polyolis poly(oxypropylene) diol or triol, and wherein said aromaticdiisocyanate is toluene diisocyanate.
 7. A curable polyurethanecomposition according to claim 6, wherein said blocking agent is one ormore compounds selected from the group comprising phenol,3-methoxyphenol, 4-methoxyphenol, nonylphenol, metacresol, para-cresol,4-chlorophenol, meta-hydroxybenzaldehyde, ortho-hydroxybenzaldehyde,para-hydroxybenzaldehyde, hydroquinone, 1-hydroxy-2-propanone,3-hydroxyacetophenone, 4-hydroxyacetophenone, ethyl acetyl acetate andcyclohexanone oxime.
 8. A curable polyurethane composition according toclaim 2, wherein said separate components are brought together and curedat an ambient temperature of from about 0° C. to about 60° C.
 9. Acurable polyurethane composition according to claim 3, wherein saidseparate components are brought together and cured at an ambienttemperature of from about 0° C. to about 60° C.
 10. A curablepolyurethane composition according to claim 7, wherein said separatecomponents are brought together and cured at an ambient temperature offrom about 0° C. to about 60° C.
 11. A curable polyurethane composition,comprising:a polyurethane prepolymer component, said polyurethaneprepolymer component being made from a polyester polyol, a polybutadienepolyol, or a poly(oxyalkylene) polyol and an aromatic polyisocyanate,said alkylene group of said poly(oxyalkylene) polyol having from 2 to 6carbon atoms, said polyurethane prepolymer having blocked isocyanategroups; a curing agent component, said curing agent component comprisingan amine curing agent containing at least two primary amines, and aneffective amount of a bicyclic amidine catalyst or a derivative thereofcapable of unblocking said blocked isocyanate groups, said catalystcomprising 1,5-diazobicyclo (4:3:0) non-5-ene (DBN).
 12. A curablepolyurethane composition according to claim 11, wherein said derivativeof said catalyst is the reaction product of said catalyst with phenol, asulfonic acid, a sulfimide, a sulfamide, a phosphonic acid, aN-sulfonylcarboxamide having a total of from 2 to 36 carbon atoms, or acarboxylic acid having from 2 to 18 carbon atoms, wherein said blockedurethane prepolymer is made with a blocking agent subsequently blockingterminal isocyanate groups, and wherein the amount of said catalyst isfrom about 0.01 to about 2.5 parts by weight per 100 parts by weight ofsaid prepolymer.
 13. A curable polyurethane composition according toclaim 12, wherein said derivative is the reaction product of DBN withphenol or 2-ethyl hexanoic acid.
 14. A curable polyurethane compositionaccording to claim 12, wherein said prepolymer is made from saidpoly(oxyalkylene) polyol, wherein said poly(oxyalkylene) polyol has anequivalent weight of from about 500 to about 3,000, wherein saidpoly(oxyalkylene) polyol optionally has ethylene oxide end blocks withthe total amount of said ethylene oxide end blocks being 10 percent byweight or less based upon the total weight of said end blockedpoly(oxyalkylene) polyol, wherein said polyisocyanate is an aromaticdiisocyanate, and wherein said amine curing agent contains a total offrom 3 to about 260 carbon atoms or is a polymer having a molecularweight up to about 5,000.
 15. A curable polyurethane compositionaccording to claim 14, wherein the amount of said catalyst is from about0.02 to about 1.2 parts by weight per 100 parts by weight of saidprepolymer.
 16. A curable polyurethane composition according to claim15, wherein said poly(oxyalkylene) polyol is poly(oxypropylene) diol ortriol, and wherein said aromatic diisocyanate is toluene diisocyanate.17. A curable polyurethane composition according to claim 16, whereinsaid blocking agent is one or more compounds selected from the groupcomprising phenol, 3-methoxyphenol, 4-methoxyphenol, nonylphenol,metacresol, para-cresol, 4-chlorophenol, meta-hydroxybenzaldehyde,ortho-hydroxybenzaldehyde, para-hydroxybenzaldehyde, hydroquinone,1-hydroxy-2-propanone, 3-hydroxyacetophenone, 4-hydroxyacetophenone,ethyl acetyl acetate and cyclohexanone oxime.
 18. A curable polyurethanecomposition according to claim 17, wherein said separate components arebrought together and cured at an ambient temperature of from about 0° C.to about 60° C.
 19. A curable polyurethane composition according toclaim 18, wherein said separate components are brought together andcured at an ambient temperature of from about 0° C. to about 60° C. 20.A curable polyurethane composition according to claim 19, wherein saidseparate components are brought together and cured at an ambienttemperature of from about 20° C. to about 30° C.